Interface alloying effects on the LO and TO phonons in Si/Ge superlattices

This is the authors' abstract. We don't add key points for this paper.

By means of a supercell technique, the Raman spectra of Si/Ge superlattices with alloyed interfaces are calculated. The appearance of the Si-Ge LO peak around 400 cm^-1, observed in Raman experiments, is found to originate from the formation of interface SiGe alloys. For two transverse polarizations the so-called interface modes are affected by the interface alloyed layers in different ways: For the perfect interfaces there is a Raman peak around 400 cm^-1 for one transverse polarization due to the contribution from the interface mode. No Raman peak around 400 cm^-1 exists in another transverse polarization. With the introduction of interface alloying, the 400 cm^-1 Raman peak existing for perfect interfaces decreases its intensity, while a Raman peak around 400 cm^-1 appears in that polarization in which there is no peak in the case of perfect interfaces.